Clarification and Application of Turbulent Mixing for Hydrogen Air Supersonic Mixing

本研究分为混合评价和混合增强两部分。首先，通过铂丝催化反应验证了超声速混合条件时间序列评价的有效性。气体氢从喷射器注入超音速自由流（马赫数1.81）。采用带铂丝和参考丝（镍丝）的w型探头，对超声速混合时间序列条件进行了评价。在保持导线温度不变的情况下，通过同时测量各电路所提供的每一功率来进行评价。具体提供给铂丝的电力取决于催化热释放率（给予氢浓度）和流动对流。同时，对镍丝的影响取决于流动对流。结果表明，随着混合的发展，这些电功率之间的相关系数增大。同时还对氦、空气和无二次注入的情况进行了调查，并与氢气注入的情况进行了比较。结果表明，利用该评价方法可以测量空气-氢超声速混合层或湍流相干运动的时间序列行为。其次，对于超声速混合增强，实验表明大尺度的流向涡旋似乎是最有利的，如质量通量波动的FFT频谱分析显示，功率谱部分遵循Kolmogorov -5/3幂律，表明流向涡旋的击穿产生了高混合功率的小尺度湍流涡旋。本文采用PIV、纹影显示、热线风速仪和CFD等方法研究了湍流涡旋的击穿过程。实验结果表明，在涡旋雷诺数ReΓ=Γ/v=1.3×10^4及以上时，流向涡旋击穿成小尺度湍流，且流向涡旋上的横向结构参与了其击穿过程。从计算分析来看，坡道上剪切层的振荡会使流向涡不稳定并导致其破裂。少

This research has two parts of the mixing evaluation and mixing enhancement.First, an experimental study was carried out to confirm the validity of time series evaluation of supersonic mixing condition by using catalytic reaction on a platinum wire. Gaseous hydrogen was injected into supersonic free-stream (Mach 1.81) from injector. Time series condition of supersonic mixing was evaluated by using W-type probe which has a platinum wire and reference wire (nickel wire). The evaluation was done by simultaneously measuring each electric power supplied by each electric circuit which kept the temperature of wire constant. Specifically supplied electric power to Pt wire depended on catalytic heat release rate (giving hydrogen concentration) and flow convection. Meanwhile that to Ni wire depended on flow convection. The result showed that correlation coefficient between these electric powers increased when mixing developed. Investigations were also conducted for helium, air and no secondary i … More njectant cases to compare with the hydrogen injectant case. The results indicated that it was possible to measure the time-series behavior of air-hydrogen supersonic mixing layer or coherent motion of turbulence by using this evaluation.Second, for supersonic mixing enhancement, experiments suggested that large scale streamwise vortices seemed to be the most advantageous, for example, FFT spectrum analysis of mass flux fluctuations showed that the power spectrum partly follows Kolmogorov's -5/3 power law, indicating that the breakdown of streamwise vortices occurred to generate small scale turbulent eddies of high mixing power. The present study examined the breakdown process of streamwise vortices by using PIV, schlieren visualization, hot-wire anemometer and CFD. The experimental results showed that the breakdown of streamwise vortices into small scale turbulence occured at the vortex Reynolds number ReΓ=Γ/v=1.3×10^4 or more, and that the lateral structure on streamewise vortices took a part in its breakdown process. From the computational analysis, the oscillation of shear layer from ramp could make the streamwise vortices unstable and cause its breakdown. Less